class Animal(object):
    def run(self):
        print('Animal is running')

class Dog(Animal):
    def run(self):
        print('Dog is running')

class Cat(Animal):
    def run(self):
        print('Cat is running')

dog = Dog()
dog.run()

def run_twice(animal):
    animal.run()
    animal.run()

run_twice(Dog())

print(len('ABC'))
print('ABC'.__len__())